The invention is related to an auto-adjustment circuit for collision detection on an Ethernet network, and especially relates to improving detection of collision signals between nodes in an Ethernet network. By the use of the auto-adjustment circuit of the present invention, the detection of data collision is more accurate so that miss detection of network transmission that affect the operation of whole network is avoided. Meanwhile, the invention can also prevent error situations that occur because of ambient temperature and production processes.
Ethernet is a type of area network that provides data transmission between computers (nodes), as shown in FIG. 1. Before users, named as A, B, C, D, E, transmit their data, Ethernet monitors whether any other user is using Ethernet or not. If not, then transmission of data is started. A detection circuit exists for detecting collisions because data may be transmitted simultaneously in some cases. The IEEE specifications definition 802.3 sets forth a detection level of a well-known detection circuit for Ethernet. However, the gap between the detection signal and the detection level is very narrow. The detection method is shown in FIG. 2, where a representation of the detection level defined in 802.3 is set forth. The detection signal 20, which represents data collision, produces a under-level pulse (dash-dot-dot line) to let all users (computers) realize that data collision has occured. If the data signal 20 does not dip under the detection level (i.e., solid line), no occurrence of data collision is indicated. However, due to the influence of ambient conditions and the variation of mass production, the following situations can occur:
(1) if the detection signal is very close to the 802.3, level or is even under this level, users (computers) may not detect that data collision has occurred. PA1 (2) if the gap between the detection signal 20 and the detection level 802.3 is too large, the detection signal 20 may not dip under the detection level even if data collision has occurred, so it will misguide users (computers) to determine that no data collision occurred and mistakes will be made during data transmission.
Both these situations are troublesome and inconvenient for Ethernet usage. They may be all right for transmit mode collision detection. But for receive mode collision detection, errors will result. There is no good way to solve the above-mentioned problem in the market. Hence, the inventor devised this invention.